/Engine/Source/Runtime/Core/Public/Containers/BitArray.h
Bits within each word are read or written in the current platform's mathematical bitorder (Data[0] & 0x1, Data[0] & 0x2, ... Data[0] & 0x100, ... Data[0] & 0x80000000, Data[1] & 0x1 ... Correctly handles overlap between destination range and source range; the array of destination bits will be a copy of the source bits as they were before the copy started.
static void MemmoveBitsWordOrder ( int32 * DestBits, int32 DestOffset, const int32 * SourceBits, int32 SourceOffset, uint32 NumBits )